Mounting device for adjustable inductors



Oct. 14,.1941. w. H. JAMES MOUNTING DEVICE FOR ADJUSTABLE INDUCTORS Filed June 5, 1940 ZNVENTOR. W/Z. FEED H JAM 5Q ATTORNE Y.

Patented Oct. 14, 1941 MOUNTING DEVICE FOR ADJUSTABLE INDUCTOBS Wilfred B. James, Chicago, 111., assignor to Johnson Laboratories, Inc., Chicago, Ill., a corporation of Illinois Application June 5, 1940, Serial No. 338,957

8 Claims.

The present invention relates to inductance tievices of the type wherein the inductance of a coil is adjusted by movement of a core of magnetic material relatively to said coil. Inductors of this type are becoming increasingly popular in the high frequency art such as, for instance, in radio receivers where they are employed to tune electrical circuits over a range of frequencies or to adjust such circuits very precisely to a predetermined frequency of operation.

In inductance devices of this type there frequently arises the problem that although cores and coils should be capable of adjustment of their relative positions, the adjustment means employed should be of such nature that the cores or coils cannot be moved accidentally. Thus, in circuits that operate at a predetermined fixed frequency it is often necessary that an inductance adjustment be available after the circuit has been assembled or even after it has been mounted in the receiver, yet unintentional displacement of the adjustment means as may occur when the device is subjected to shocks during practical use or repair work, should be effectively prevented.

It is an object of the present invention to provide an inductance device of the type referred to, including means for changing the position of the core relatively to the coil which is of such nature that it provides the necessary ease of operation with adequate restraint against accidental displacement. It is another object of the present invention to provide mounting means for adjustable cores or coils 'in devices of the type referred to which permit of controlling the ease of adjustability of the movable elements at will.

Movable core inductors of the type referred to are frequently used in assemblies of two or more, so disposed relative to one another as to provide inductive coupling between two or more circuits.

It is another object of the present invention to provide cheap and yet efficient mounting means for a plurality of adjustable core inductors wherein the ease of adjustability of all movable parts may be controlled by operation of a single element.

According to the invention the movable part of a magnetic core inductor of the type referred to is provided with a screw-threaded operating rod extending through, and engaging a palnut which forms its bearing, two members being disposed at either end of said palnut and means being provided for moving said members towards one another in order to determine, by the pressure which they exercise upon opposite ends of the palnut, the ease with which said screwthreaded operating rod may be turned. In a preferred form the inductance device of the present invention includes a tube of insulating material upon which is mounted a coil and within which is movably disposed a magnetic core. This tube engages an opening provided in a carrier plate upon which is mounteda palnut that forms the bearing for a screw-threaded operating rod connected to the core, an additional plate which is parallel to the carrier plate being disposed above said palnut and screw-threaded means being provided for forcing said plates towards one another.

In practical embodiments this additional plate may be formed by one of the walls of the shield can that usually encases inductance devices of the type under discussion, and one of the screws ordinarily employed for mounting such an inductance device in a shield can may be so arranged as to move said mounting plate towards the shield can wall when it is turned, thus providing means for controlling the pressure applied upon the palnut without the aid of any other elements but those normally used in shielded inductance devices.

When a plurality of adjustable inductance devices are housed within the same shield can, as is frequently the case when two or more circuits are inductively coupled with one another, separate locking devices for fixing the position of each adjustable core or coil are no longer necessary because all operating rods may be controlled by the screw-threaded member adapted to move the carrier plate towards the shield can.

Moreover, the palnuts employed in the arrangement of the present invention are considerably cheaper than the bearings heretofore in use for screw-threaded operating rods of adjustable inductance devices and the like.

The invention will best be understood by reference to the accompanying drawing illustrating a preferred embodiment thereof and wherein Fig. 1 shows an intermediate frequency transformer embodying the present invention, in vertical central section,

Fig. 2 shows a detail of the device of Fig. l on an enlarged scale, and

Fig. 3 is a plan view of a palnut such as may be employed in arrangements of the present invention.

The intermediate frequency transformer shown in Fig. 1 consists of two circuits that are tuned to substantially the same frequency. Transformcm of this type are used in superheterodyne receivers or the broadcast reception art.

The inductance device of Fig. 1 possesses a mounting or carrier plate I of metal or any other suitable material. This mounting plate is provided with two openings 2 and 3 which receive the upper ends of two tubes t and 5 of cardboard, Bakelite or any other suitable insulating material. Tubes 6 and it slightly protrude above the upper' surface of carrier plate 8 and are flanged out over said carrier plate to somewhat overlap the circumference of openings 2 and 3. The bottom ends of tubes 6 and 8 may be similarly secured to openings in a base plate 5 of metal or insulating material.

Tubes s and L: carry inductance coils I and 8 respectively which, in the particular embodiment shown, are of the universal type. Said tubes contain cores 9 and Id respectively which consist of minute insulated particles of a magnetic materialthat have been compounded into solid bodies with or without a suitable binder. Cores of this type are now generally in use in inductance devices of the high frequency art and have been described in detail in many publications such as, for instance, in U. S. Patent No. 1,982,689 to W. J. Polydorofi. Said cores are provided with screw-threaded operating rods I i and I2 respectively which are preferably molded into the core bodies during their manufacture.

Coils i and 3 together with their cooperating cores 9 and it are mounted at diiierent. altitudes vertically at such a distance apart as will provide the desired small amount of inductive coupling that is required in devices of this type. When inductors are in such a position relative to one another there'is a smaller amount of coupling between them than would exist if they were mounted coaxially. For this reason their vertical separation may now be considerably smaller than previously necessary, which materially reduces the height of the complete device.

Operating rods II and i2 protrude through,

' and engage palnuts i5 and it respectively which rest upon the flanged upper ends I3 and M of insulating tubes :3 and 5.

By the term palnut I mean a type of nut as shown in greater detail in Figs. 2 and 3 and which is commonly known under this term today. Palnuts are usually made of spring sheet metal and in their simplest form they consist of a vertical circumferential portion Ida (Figs. 2 and 3') to which is joined an arched portion I517 having an opening H50 in its center. The circumference of this opening IE0 is interrupted by a radial incision 85d which permits the arched portion i5b to be bent in such a manner that the two opposite edges I5e and ibj formed by incision 55d and center opening E50 terminate at different planes corresponding to two successive threadson the screw-threaded rod on which the palnut turns. Thus, the circumferential line of center hole I50 is helical and forms a single-threaded nut. As pressure is applied to arched portion I51), for instance, when the' nut is tightened against a surface, the arch is somewhat flattened, wherebythe central edge of arched portion I5!) closes in and grips screw-threaded rod II.

More than one incision'may be provided in the central edge of arched portion I5b forming a series of prongs that engage one or more threads of the' screw bolt. Any one of these nuts may be used for the purposes of the present invention.

Reverting now to Fig. 1, palnuts I5 and I6 are placed upon flanges I3 and I4 respectively of tubes 4 and 5 with the arched portions ISb and l6b protruding into the openings of the tubes.

The complete assembly described above is encased in a shield can i! of the type commonly employed for shielding inductane devices of the slotted head on the outside of shield can Ii.

With screw bolt 22 loose and the upper wall 58 of shield can H resting only loosely upon the palnuts i5 and E8, the operating rods II and I2 arefreely rotatable, but when head 24 of bolt 22 is tightened against wall I8 of shield can I! said wall I8 and carrier plate I will exercise increasing pressure upon palnuts l5 and I6 and 7 force their arched portions against flanges l3 and Id of insulating tubes 6 and 5. Consequently the arches of palnuts I5 and It will tend to flatten and will grip tightly theroots of the screw threads of operating rods II and I2 thus restraining these rods against free rotation while still permitting them to be turned, for vertical movement of the cores, when properly engaged by a screw driver, pliers or other means capable of transmitting proper rotational force. By turning screw bolt 22 any desirecl'ease of operation and any desired degree of restraint against accidental displacement may. be established for screw-threaded rods I i and I2.

In the specific example above described the arrangement is such that the inductance coils are stationary and that the operating rods are secured to, and move the cores. The present invention is equally applicable to all such devices where the cores are stationary and the coils are moved relatively to the cores.

While I have above described my invention as applied to two movable elements it will be understood that it is equally applicable to more than two movable elements or to a single one. In case that the function of more than one operating rod is to be controlled as in the specific example described above it is desirable that the means for moving the members which bear pressure upon the palnuts, be centrally positioned relative to whatever number of operating rods are to be controlled in order that the pressure exercised by said means be evenly distributed.

While I have shown my invention in the particular embodiment above described, it will be understood that I do not limit myself thereto but that I may employ equivalents without departing from the scope of the appended claims.

Having thus described my invention what I claim is:

1. The combination of a screw-threaded operating rod, a palnut forming the bearing for said screw-threaded rod and two elements disposed at either end of said palnut and means for pressing said elements against said palnut to determine the ease of turning said operating rod.

2. A mounting device'including a carrier plate, a tube secured to said carrier plate, a movable body arranged within, and guided by said tube, said body having a screw-threaded operating rod protruding through said carrier plate, a palnut resting upon said plate and forming a bearing allel to said carrier plate and situated at the other end of said palnut, and screw-threaded members adapted to press one of the said plates against said palnut.

3. A mounting device including a carrier plate having an opening, a tube engaging with one of its ends said opening, said tube end being flanged over the circumference of said opening, a body movably arranged within, and guided by said tube, said body having a screw-threaded operabsaid palnut and means for approaching said plates to compress said palnut.

4. A mounting device including a casing, a car-- rier plate mounted in said casing in parallel relation to one or its walls, a tube secured to said carrier plate, a body movably arranged within, and guided by said tube, said body having a screw-threaded operating rod protruding through said carrier plate and said parallel wall of the casing, a palnut resting upon said carrier plate and below said parallel wall of the casing and forming a bearing for said operating rod, and a screw-threaded member extending from said carrier plate and protruding through said parallel wall and adapted .to move said carrier plate and said wall towards one another topress against said palnut.

5. The combination or a plurality oi screwthreaded operating rods, an equal number of palnuts forming bearings for said screw-threaded rods, two elements disposed in parallel relation and. at either end of said palnuts, and screwthreaded means disposed in a central position relative to said operating rods and adapted to 6. A mounting device including a carrier plate, a plurality of parallel tubes secured tosaid carrier plate, a body movably disposed in each tube, all bodies having screw-threaded operating rods protruding through said carrier plate, a plurality of palnuts resting upon said plate and forming bearings for said operating rods, an additional plate parallel to said carrier plate and situated at the other ends of said palnuts, and a screwthreaded member'protruding through both plates and adapted to move said plates towards one another to press against said palnuts. I

7. A mounting device including a carrier plate having a plurality of openings, a plurality of tubes each engaging with one of its ends one of said openings, said tube ends being flanged over the circumferences of said openings, a movable body disposed within each tube, screw-threaded operating rods extending from said bodies, palnuts resting upon the flanged ends of said tubes and forming bearings for said screw-threaded operating rods, an additional plate parallel to said carrier plate and at the other end of said palnuts, and means for forcing said plates towards one another.

8. A mounting device including a casing, a carrier plate mounted within said casing parallel to one of its walls, a plurality of parallel tubes secured to said carrier plate, a body movably disposed within each tube, each of said bodies having a screw-threaded operating rod protruding through said carrier plate and said parallel wall or the casing, a plurality of palnuts resting upon said carrier plate and forming bearings for said operating rod, a screw-threaded member extending irom said carrier plate and protruding through said parallel wall and adapted to move said carrier plate towards said wall, to press against the ends of said palnuts and to firmly move said elements towards one another to press 40 hold said carrier plate and said casing together.

against said palnuts.

WIIFRED H. JAMES. 

